Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A time-slotted channel hopping (TSCH) network, for example as defined by IEEE 802.15.4, can provide a communications network for resource providers (e.g., utility companies, home automation providers, industrial automation providers, etc. The resource providers may use the TSCH network to communicate between TSCH nodes (e.g., electric meters, routers, etc.), or endpoints (EPs), and low-energy (LE) devices, or LE endpoints (LEEPs), used to monitor or manage consumption of resources (e.g., electricity, heat, water, etc.). In some cases, LEEPs can be Internet-Of-Things (IoT) enabled devices that can be used in smart power grid and smart home technologies.
Currently in TSCH networks, there is a concept of “links” where there are, for example, guaranteed timeslots for nodes to transmit beacons for timeslot synchronization, and contention access period (CAP) timeslots for general communication of both unicast or broadcast messages. A unicast message is a message transmitted to one other node on the network. A multicast/broadcast message is a message transmitted to a group of nodes on the network. Although nodes use clear channel assessment (CCA) to validate that a channel is available, this only protects the channel from competing devices that are not time-synchronized, and as such does not inhibit nodes within the same personal area network (PAN) from interfering with each other's communication.
In the case of two (or more) nodes simultaneously transmitting frames, none will successfully transmit that frame. If those frames are unicast packets, there will be a media access control (MAC) layer retry that will retry in a random back-off period if the MAC layer acknowledgement from the destination node is not received. If one or more of the simultaneously transmitted frames is a broadcast frame, there is no logic to acknowledge the broadcast frame. Thus, the broadcast frame may never be received by other nodes and the transmitting node has no way of knowing if the frame was received by other nodes.